The association between smoking and knee osteoarthritis in a cohort of Danish patients undergoing knee arthroscopy.

BACKGROUND: It has been suggested that smoking is associated with reduced risk of knee osteoarthritis (OA). However, supplementary studies are needed to further investigate any such potential association. Thus, our aim was to examine the relationship between smoking and early or more established knee OA in a cohort of relatively young patients with meniscal tears. METHODS: This cross-sectional study included 620 participants from the Knee Arthroscopy Cohort Southern Denmark (KACS) undergoing knee arthroscopy for a meniscal tear (mean age 49.2 (18.0-76.8) years). Recruitment of patients was performed between February 1, 2013, and January 31, 2015, at four different hospitals in Denmark. We defined early or more established knee OA as the combination of patient-reported frequent knee pain, degenerative meniscal tissue and presence of cartilage defects assessed by the operating surgeons. The relationship between smoking status and knee OA was examined by risk ratio (RR) with a 95% confidence interval (CI), estimated from logistic regression adjusted for age, sex, BMI, education, work status and level of physical activity. RESULTS: The prevalence of early or more established knee OA was 37.7% in current smokers and 45.0% in non-smokers. We found no statistically significant association between current smoking and knee OA (adjusted RR 1.09, 95% CI 0.91-1.30). CONCLUSIONS: This study found no relationship between current smoking and early or more established knee OA in a cohort of patients undergoing arthroscopic meniscal surgery. Thus, the inverse association between smoking and knee OA that has been suggested by previous studies was not confirmed.

Impaired postural balance in the morning in patients with knee osteoarthritis.

Postural balance (PB) is frequently used as an outcome measure in clinical and research settings when assessing patients with knee osteoarthritis (OA). Pain and stiffness is known to affect PB, and is elevated in the morning and evening in OA patients. The aim of this study was to explore if time-of-day affects PB control in knee OA patients. Centre Of Pressure (COP) excursion was measured (100Hz) by force plate technique at selected time-points (9.00 a.m., 12.30 p.m. and 4.00 p.m.) during a single day in 32 knee OA patients aged 66.0 (10.3) years. A rigorous protocol was followed to ensure comparable testing conditions across time-points. PB control was quantified by the COP variables: velocity moment (mm(2)/s), total sway area (mm(2)), total sway length (mm) and confidence ellipse area (mm(2)). A two-way mixed-effects model showed that PB significantly improved between 9.00 a.m. and 12.30 p.m. in three out of four COP variables. The observed improvement was 11.9% (p=0.011) for velocity moment, 12.2% (p=0.011) for total sway area and 9.4% (p<0.001) for total sway length. PB appears to be impaired in the morning relative to midday in knee OA patients. Thus, it is recommended that time of assessment is standardized between sessions when assessing PB in clinical and research settings in knee OA patients.